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Monday, 23 October 2017

Quantum theology

Schrodinger's cat

I have noticed, among a few people, attempts to drag quantum mechanics, or other laws of physics, into discussions of theology. Specifically, the implications of Schrodinger's cat.

The issue is what QM calls "decoherence". QM says that the cat is in a superposition of two states, alive and dead. Common sense tells us that can't be true, and when we open the box, we find a cat that is either alive or dead but not both.

Common sense is not a good guide when dealing with things that we don't commonly experience. And Richard Feynman said "If you think you understand quantum mechanics, you don't understand quantum mechanics."

Quantum theologians interpret Schrodinger's cat as meaning that the presence of a conscious observer is what causes the decoherence, the collapse of the superposition of states into a single state (but see Feynman, above). And they also point to the fact that by Heisenberg's uncertainty principle, you cannot precisely know both the position and momentum of a particle.

They then jump from "conscious observer for the cat" to a supposed need for a conscious observer for every particle in the universe. And therefore God. But see Feynman, above. You don't actually need a conscious observer.

But I was eating lasagne today when I had a sudden thought, and the fork paused halfway between the plate and my mouth, a situation which rarely arises.

Suppose there was an omnipresent, omniscient observer in the universe. Then the double-slit experiment (DSE) wouldn't give the result that it actually gives! Which would demonstrate the impossibility of an omnipresent, omniscient observer in the universe. Or at least, it would be pretty strong evidence against such an observer.

So let's run through the double-slit experiment and its implications. And let's start with the fact that, unlike the cat experiment (it would be too cruel), the double slit experiment has been done, many times, with reproducible results. And you can do it yourself!

The double slit experiment

So you thought that the Trinity was a mystery? The double slit experiment (DSE) really is a mystery. Richard Feynman called it "a phenomenon which is impossible […] to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery [of quantum mechanics]."

You can read about it here. https://en.wikipedia.org/wiki/Double-slit_experiment
There's a youtube video that explains this in an easy-to-understand way.

https://www.youtube.com/watch?v=DfPeprQ7oGc

And here's the thing. It looks as if the observer affects reality. In the absence of an observer, particles can act as waves, and give the interference effects of the DSE. But if an observer watches the particles going through the slits, particles can only act as particles - there's no interference.

And that where Quantum Theology comes in, claiming that consciousness affect reality. That's because they don't understand what is meant by an observer (an observer doesn't have to be conscious) and they don't understand QM (See Feynman).

But now consider this.

Suppose there is an omniscient god. Then there is *always* an observer, and so matter (and light) would *always* behave as particles, and the DSE would never show interference.

And yet it does. And you can confirm that for yourself; this is an experiment that you can do at home. All you need is a laser pointer, aluminium foil (such as is used for baking) and some paper.

For those who don't know what the Quantum Zeno effect is, basically the more you measure a system, the lower the probability of that system changing from a measured initial state. Those tiny quantum kettles, if watched, never boil, kiddies. So if an omnipresent omniscient 'god' was actually observing all the time, the system (in this case a radioactive particle) couldn't change state sufficiently to decay. There could never be radioactive decay, which would be a problem, obviously. RRD

However, in the context of Yakir Agaronov's week measurements, the perturbations of a measurement does not need to be so great as to collapse the wave function. So God could still be watching but just doesn't change anything unless he stares too intently.

If you can accept that the wave nature of matter reflects its natural state and its particular nature arises from environmental interactions, the following may be of interest to you:

It isn't the size of the perturbation that matters, it is the fact of the observation that collapses the wave function. So no matter how weak a God is, if he detects the slit travelled, the double-slit experiment doesn't produce an interference pattern.